definition of electrolysis
the breaking own of a compound into its elements using an elements using an electric current
what is electrolysis often used for
extract metals from their metal ores
purify metals
produce non-metals
what is the circumstance under which metals are extracted electrolysis
when metals cannot be extracted by heating their ores with carbon
what is electrolysis carried out in
an electrolysis cell
what does an electrolysis cell consist of
an electrolyte
2 electrodes
power supply
what is an electrolyte
the compound that is broken down during electrolysis, either a molten ionic compound or a concentrated aqueous solution of ions
what are electrodes
metal or graphite rods that conduct electricity to and away from the electrolyte
the positive electrode
anode
the negative electrode
cathode
what kind of current must the power supply of the electrolysis cell have
direct
where cations gain electrons
negatively charged cathode
which redox reaction takes place at the cathode
reduction
what happens when a metal is formed at the cathode
metal deposited on the cathode
forms a molten layer
observation when hydrogen gas is formed at the cathode
bubbles are seen
where anions lose electrons
positively charged anode
which redox reaction takes place at the anode
oxidation
true/false
aqueous solutions have more than one cation and anion in solution due to the presence of water
true
which ions does water contribute to a solution
H+ and OH-
why does water splits into H+ and OH- during electrolysis
it is a weak electrolyte
what the actual ions that are discharged during electrolysis depend on
the relative electrode potential of the ions
the concentration of ions
what is the relative electrode potential of ions
describes how easily an ion is discharged during electrolysis
what property must a positively charged cation have tobe discharged first at the cathode
the most positive relative electrode potential
why will the the positively charged cation with the most positive electrode potential be discharged first
it is the most easily reduced
when working with a concentrated aqueous solution of NaF, what will be discharged at the cathode and why
H+ ions because they have a higher relative electrode potential the Na+
what property must the negatively charged anion have to be discharged from anode first
the most negative relative electrode potential
why must the anion have the most negative relative electrode potential in order to be discharged first from the anode
it is most easily oxidised
when working with a concentrated aqueous solution of NaF, what anions will be discharged first at the anode and why?
F- since they have a lower relative electrode potential than OH-
during electrolysis what influences the likelihood of discharge of ions at the electrodes
the concentration of ions as they are proportional
when working with a concentrated solution of NaF during electrolysis, why are more (mainly) fluoride ions discharged at the anode
fluoride ions are in higher concentration
when working with a very dilute solution of NaF during electrolysis, why will a mixture of both oxygen and fluorine gas be formed at the anode
there is much more oxygen and much less fluorine available
what type of reaction is electrolysis
a redox reaction
what must always balance when writing electrolysis equations from both electrodes
electrons